In recent years, rapid advances have been made in digitalization of information. This has led to remarkable efforts to meet with this in the imaging field.
In particular, as symbolized by the digital camera, in the imaging surfaces, conventional film is being taken over by use of solid-state imaging elements such as CCDs (charge coupled devices) or CMOS (complementary metal oxide semiconductor) sensors in most cases.
An imaging lens device using a CCD or CMOS sensor for the imaging element in this way optically captures the image of an object by the optical system and extracts the content as an electric signal by the imaging element. Other than a digital still camera, this is used in a video camera, a digital video unit, a personal computer, a mobile phone, a personal digital assistant (PDA), an image checking device, an automatic control use industrial camera, and so on.
FIG. 1 is a diagram schematically showing the configuration of a general imaging lens device and a state of light rays.
This imaging lens device 1 has an optical system 2 and a CCD or CMOS sensor or other imaging element 3.
The optical system includes object side lenses 21 and 22, a stop 23, and an imaging lens 24 sequentially arranged from the object side (OBJS) toward the imaging element 3 side.
In the imaging lens device 1, as shown in FIG. 1, the best focus plane is made to match with the imaging element surface.
FIG. 2A to FIG. 2C show spot images on a light receiving surface of the imaging element 3 of the imaging lens device 1.
Further, imaging devices using phase plates (wavefront coding optical elements) to regularly disperse the light rays, using digital processing to restore the image, and thereby enabling capture of an image having a deep depth of field and so on have been proposed (see for example Non-patent Documents 1 and 2 and Patent Documents 1 to 5).
Further, an automatic exposure control system of a digital camera performing filtering using a transfer function has been proposed (see for example Patent Document 6).
Non-patent Document 1: “Wavefront Coding; jointly optimized optical and digital imaging systems”, Edward R. Dowski, Jr., Robert H. Cormack, Scott D. Sarama.
Non-patent Document 2: “Wavefront Coding; A modern method of achieving high performance and/or low cost imaging systems”, Edward R. Dowski, Jr., Gregory E. Johnson.
Patent Document 1: U.S. Pat. No. 6,021,005
Patent Document 2: U.S. Pat. No. 6,642,504
Patent Document 3: U.S. Pat. No. 6,525,302
Patent Document 4: U.S. Pat. No. 6,069,738
Patent Document 5: Japanese Patent Publication (A) No. 2003-235794
Patent Document 6: Japanese Patent Publication (A) No. 2004-153497